The invention relates to an internal combustion engine having an exhaust gas turbocharger and an exhaust gas recirculation system including a turbine with two separate inlet passages each connected to an engine exhaust line.
DE 102 45 388 A1 describes a supercharged internal combustion engine having an exhaust gas recirculation system. The exhaust gas turbine of the exhaust gas turbocharger has two flow passages with flow cross sections of different size, which are separated from one another by a dividing wall and are each supplied with exhaust gases from a respective cylinder bank of the internal combustion engine via separate exhaust lines. The different flow cross sections create a different pressure in the flow passages of the exhaust gas turbine. This pressure differential can be used to improve the exhaust gas recirculation by having a return line branching off from the exhaust line of the smaller flow passage, in which a higher pressure prevails, to the intake manifold, so that, particularly at low to medium loads and engine speeds of the internal combustion engine, exhaust gas from this exhaust line can be transferred into the intake manifold, where it is thoroughly mixed with the combustion air intake. This makes it possible to reduce the NOx emissions, especially during partial load operation of the engine.
The two exhaust lines between the two cylinder banks of the internal combustion engine and the flow passages of the exhaust gas turbine are connected to one another by a bypass line, in which a one-way flow valve is arranged, which will only allow an exhaust gas flow from the exhaust line of the larger flow passage towards the exhaust line of the smaller flow passage. Pressure pulses in the exhaust line of the larger flow passage, which briefly exceed the exhaust counter-pressure in the exhaust line of the smaller flow passage, can be used to transfer exhaust gas into the exhaust line of the smaller flow passage, with the result that the pressure level in this line can also be increased and an exhaust gas recirculation can be performed over larger operating ranges. The pressure regulation in order to prevent inadmissibly high pressures is achieved by means of a bypass line, which in bypassing the exhaust gas turbine branches off from the exhaust line of the smaller flow passage and which can be adjusted by way of a controllable shut-off valve.
Based on the state of the art, it is the object of the present invention to facilitate exhaust gas recirculation over wide operating ranges by means of simple design measures. At the same time, it is intended to provide an effective overload protection, especially in the upper load and engine speed range, both in fully firing drive operation and in engine-braking operation.